Multilevel Converter based PV-STATCOM with Global Maximum Power Point Tracking at Low Voltage during Partial Shading

The conventional photovoltaic-converters are usually a 2-stage converter, consisting of a DC-DC stage for MPPT operation followed by a central inverter for grid or load side control. This configuration faces difficulty when Global Maximum Power Point (GMPP) is located at lower voltage due to partial shading. In this paper, a configuration with single-stage power conversion and multilevel voltage pattern is proposed which offers three advantages like (i) low overall losses, and hence, improved efficiency, (ii) no need of ac-side passive filters, and (iii) capability to operate at low-voltage maximum power point. A multilevel converter is used where PV panels are directly conneted to each submodule. This paper focuses on the over-modulation situation in the submodule(s) due to voltage dip in the corresponding DC bus during partial shading. An Auxiliary submodule fed from tertiary winding of power transformer is incorporated to address the issues at low voltage GMPP. A technique to control active and reactive power of individual submodules is developed. The proposed topology and the control method are validated through MATLAB/Simulink and the results show satisfactory performance.